3. Required standards
3.1 Advertisements will not be approved for, or permitted to remain on
TfL’s services if, in TfL’s reasonable opinion, the advertisement falls
within any of the following categories.

(a) The advertisement does not comply with the law or incites someone to break the law.

(d) The advertisement is likely to cause widespread or serious offence to members of the public on account of the nature of the product or service being advertised the wording or design of the
advertisement or by way of inference.

(k) The advertisement contains images or messages which relate to matters of public controversy and sensitivity.

(n) The advertisement is likely to be defaced due to the subject matter or due to the inclusion of a high proportion of blank
space.

(o) The advertisement may adversely affect in any way the interests
of the site owner.

If you know people in London, why not ask them to keep their eyes peeled, and report back to you any sightings of the ad (exact location i.e. station/line, date). The Underground is a big place, and everyone takes different journeys.

That's an interesting argument to make, "I'm compelled to deface Scientology adverts so you shouldn't have them up. Look, just watch. Put up an advert and I'll be compelled to apply stickers to it or write on it with a Sharpie. I CANNOT HELP MYSELF! Nor can other people in London, so you should just take them down."

That's an interesting argument to make, "I'm compelled to deface Scientology adverts so you shouldn't have them up. Look, just watch. Put up an advert and I'll be compelled to apply stickers to it or write on it with a Sharpie. I CANNOT HELP MYSELF! Nor can other people in London, so you should just take them down."